In the field of electric home appliances and computer mobile products, high functionalization is required in the tendency of lighter, thinner, and more compact. The tendency of high functionalization exists also in the card industry. For credit cards and cash cards used heretofore, a main stream of recording data has been embossing and magnetic stripes. However, high functionalization has recently been paid attention, such as multi-function settlements for credits, electronic money and the like by IC cards.
In order to deal with the tendency of this type, a large capacity and a high density have been required for IC chips. The development of enciphering technologies for processing important information and high-speed signal processing technologies among others are made vigorously. Further, not only reading/writing a large amount of information from/in cards, a number of types of various applications have been proposed to positively utilize the information in cards, and a variety of usage types are being born. As the usage types change in various ways, the present circumstance of product qualities of IC cards is a high necessity of satisfying product qualities in various environments/fields, in addition to high security and high-speed processing performance made to date (for example, Japanese Patent Application Publications Nos. HEI-6-336095 and HEI-9-27839 and Japanese Patent Application Publication No. 2001-53487).
As the usage types change in various ways, in addition to high security and high-speed processing performance, qualities required for IC cards are increasing. Among others, the qualities suitable for usage types of portable communication terminals typically IC cards and portable phones are urgently required to become satisfactory, because it is anticipated that the number of users increases rapidly.
Services based on usage types are being developed rapidly, such as confirming record contents (e.g., a card balance) of an IC card by using a display function of a portable communication terminal having a built-in IC card reader/writer. If communications of portable phones and communications between an IC card and a reader/writer are made at the same time, such as an incoming call during a read operation for card information and communications between the IC card and reader/writer during phone service, two communication waves are picked up in the IC card and may be synthesized as a mixed modulation wave in the IC card. There is a possibility that this mixed modulation wave operates as noises on a reception wave of the portable phone, resulting in an incoming call defect, a phone service defect and the like.
If the mixed modulation wave is picked up around a transmission frequency (e.g., 900 to 940 MHz) of a portable phone, the resultant waveform becomes as shown in FIG. 3A. Smaller waveforms are generated on the right and left sides of FIG. 3A in some cases. Waveforms in the left side in FIG. 3A particularly have a high possibility of influencing a reception frequency (843 to 885 MHz) of the portable phone, as noises. In this case, the communication function essential for a portable phone cannot be retained and there is a concern that a speech function of the portable phone and a read/write function of the IC card are limited to a certain extent.
The present invention has been made in consideration of the above-described problems, and has an issue of providing an IC card capable of suppressing radio waves generated during communications between portable phones and communications between an IC card and a reader/writer from inputting to an IC chip, suppressing radio waves mixedly modulated in the IC chip from outputting, and excluding adverse effects on an operation of peripheral apparatus such a portable phones, and its manufacturing method.